Exhaust duct part in particular for an internal combustion engine

An engine comprising at least two exhaust outlets, each of said at least two exhaust outlets having attached thereto a respective exhaust duct part for outflow of exhaust gases from the engine, each said exhaust duct part comprising a continuous elongated external casing having a constant cross section throughout substantially an entire length thereof, and at least one acoustic attenuation unit positioned within said external casing at a location such that a fluid transfer section of said external casing that leads to said acoustic attenuation unit is of a length sufficient to enable said fluid transfer section to participate in providing acoustic attenuation for said exhaust duct part, said acoustic attenuation unit comprising an elongated internal casing adapted to include sound deadening material and having an outer surface that defines with an inner surface of said external casing at least one longitudinal channel defining therein a space for the passage of the exhaust gases, the improvement wherein:

• said internal casing has a transverse cross-sectional configuration that is of substantially constant area throughout substantially an entire length of said internal casing;
• said at least one longitudinal channel is defined by at least a portion of said internal casing being in contact with said inner surface of said external casing;
• and
• said portion of said internal casing which is in contact with said inner surface of said external casing, comprising at least one zone of said internal casing deformed radially outwardly along substantially said entire length of said internal casing and defining a radially outwardly projecting space within said internal casing so as to create an increased surface contact area between said acoustic attenuation unit and said space defined within said at least one longitudinal channel, said outwardly projecting space being adapted to include the sound deadening material.

An apparatus comprising:

• an elongated exhaust duct having a continuous elongated external casing having a substantially constant transverse cross-section along substantially an entire length thereof;
• at least one acoustic attenuation unit mounted within said external casing and comprising an elongated internal casing adapted to include sound deadening material and having an interior, an outer surface, a substantially constant transverse cross-section along substantially an entire length of said internal casing, and at least one elongated zone, formed along substantially said entire length of said internal casing, said zone being deformed radially outwardly and defining two elongated sidewalls that form an internal space in communication with a remainder of said interior of said internal casing, an outer surface of said at least one elongated deformed zone contacting an inner surface of said elongated external casing, said internal space being adapted to include the sound deadening material;
• and
• at least one elongated longitudinal channel through which exhaust gases are adapted to flow being defined by said outer surface of said at least one elongated zone, a remainder of said outer surface of said elongated internal casing and said inner surface of said elongated external casing.

A process for providing acoustic attenuation for an exhaust duct part, said process comprising the steps of:

• providing a continuous substantially rectilinear elongated external casing having a constant cross section throughout substantially an entire length thereof;
• providing at least one elongated acoustic attenuation unit comprising an elongated internal casing adapted to include a sound deadening material and having a transverse cross-sectional configuration that is of substantially constant area throughout an entire length of said internal member, with said box member having at least one radially outwardly deformed zone that extends over substantially said entire length of said internal casing and defines a radially outwardly projecting space within said internal casing adapted to include the sound deadening material;
• and
• fixedly positioning said internal casing within said external casing with an outer surface of said at least one deformed zone being in contact with an inner surface of said external casing, and thereby defining between said inner surface of said external casing and an outer surface of said internal casing at least one longitudinal channel for passage therethrough of the fluid.